First and foremost this is NOT a weight loss diet. It is a "cleanse" and the system will do what it needs to do the most 1st to heal and repair. Further more of those 8 lbs I would say 4 or so will be just the emptying of your bowels of food and debris. Even then 4 Lbs loss over 2 weeks is perfectly acceptable weight loss. Rapid weight loss in neither healthy nor permanent without a concentrated and focused major life style change. There are no magic bullets.
The issue of what is claimed in the book in regard to weight has been flogged to death in this forum a zillion times. The book is very vague in many issues and there are a number of things that have now become regular and established norms that have come about from the collective experience of thousands that have gone through forums like this and are not mentioned in the book. The Weight Loss FAQs
As stated in the FAQS the primary focus of any successful weight loss program is and will always be balanced nutrition and exercise. The END. There are no short cuts. The MC and all these other cleanses and just "TOOLS" that help the system get rid of built toxins and other other debri that prevent the system from operating and maximum efficiency. You are not going to clean out a lifetimes worth of abuse and accumulated waste in 2 weeks. not even 40 days. That is just a "good start". Any and all success hinges ultimately on what you put back in the system after you clear the garbage out. There is no way around this. It will be gradual. If you focus on the cleanses as "the" solution you WILL fail. No if ands or buts about it.
What you term "lack of success" I would say is very heavily tainted by the "quick fix" mentality ingrained on the masses by the big commercial Pharma industries. There simply are no quick permanent cures or weight loss without the rebuild process required period.
Plain ole common sense dictates that you are not going to fix and expel a lifetimes worth of accumulated waste matter aaaaaand regenerate damaged cells in a short time without a radical lifestyle change and a rebuilding period of putting back in balanced and concentrated nutrition and regular exercise to "allow" the system to "heal itself" and revert to it natural state of health. This will take time and a concentrated conscious effort and educating yourself and most of all experimenting till you find what works for you. There is no way around this. The cleanses ain't "IT"
It will be what it will be for you. Your success does not lie in any expectations but just in the fact that you have made a "conscious choice" to cleanse your system. Don't expect anything but focus on the bigger picture and educating yourself. The longer fast will not only work on a much deeper cleansing level but the effort itself and the will to do it will help cement the resolve to continue on with the required lifestyle change. Read the Detox Stages in the FAQs you some insights on the cleansing timeline